The invention relates to regulating or adjusting methods and apparatus, and more particularly to improvements in methods of and apparatus for effecting movements of one or more mobile components to any one of a plurality of different positions. For example, the improved method and apparatus can be resorted to for selecting and/or changing the positions of one or more mobile parts of a change-speed transmission in the power train of a motor vehicle. Still more particularly, the invention relates to improvements in cylinder and piston units wherein a mobile part (such as one or more pistons) is movable in a housing or body between two or more different positions.
It is often necessary to move one or more components of a prime mover or a motion transmitting unit between two or more positions and to reliably retain the component(s) in the selected position(s). Examples of such apparatus are so-called actuators, i.e., devices which can perform an action or can output signals in response to signals from a control system (e.g., a computer). Heretofore known apparatus of the just outlined character normally comprise or constitute electric stepping motors or fluid-operated (hydraulic or pneumatic) cylinder and piston units. A drawback of such conventional apparatus is that their controls are rather complex, expensive, bulky and/or (often) unreliable. As a rule, or at least in many instances, the controls include or constitute one or more circuits designed to compare the desired position(s) of one or more mobile components with the actual position(s), and to transmit to the actuator signals at least when the desired position(s) departs or depart from the actual (ascertained or monitored) position(s). In addition to the circuit(s), such control systems must embody one or more position- or movement-monitoring sensors, auxiliary circuits and/or others.